package utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class MD5 {
  private static MessageDigest _mdInst = null;
  private static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
  private static MessageDigest getMdInst() {
    if (_mdInst == null) {
       try {
        _mdInst = MessageDigest.getInstance("MD5");
       } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
       }
    }
   return _mdInst;
  }
  public static String encode(String s) {
    try {
      byte[] btInput = s.getBytes();
      // 使用指定的字节更新摘要
      getMdInst().update(btInput);
      // 获得密文
      byte[] md = getMdInst().digest();
      // 把密文转换成十六进制的字符串形式
      int j = md.length;
      char str[] = new char[j * 2];
      int k = 0;
      for (int i = 0; i < j; i++) {
        byte byte0 = md[i];
        str[k++] = hexDigits[byte0 >>> 4 & 0xf];
        str[k++] = hexDigits[byte0 & 0xf];
      }
        return new String(str);
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
  }
}
